Pipe joint

ABSTRACT

A pipe joint which is made of a hollow body member having a passageway therethrough for receiving a pipe, a segmented gripper means positioned in a first circumferential tapered channel in the hollow body member and moveable axially within the passageway. The arrangement is such that, in use, when forces are applied tending to separate the pipe from the hollow body member the segmented gripper means can move axially along the tapered channel into gripping engagement with the pipe.

This is a continuation of International Patent Application No.PCT/GB96/01879, with an international filing date of Aug. 2, 1996, nowpending.

This invention relates to pipe joints, and more particularly to a pipejoint comprising a hollow body member having a passageway therethroughfor receiving a pipe into engagement therewith.

A very large number of pipe joints have been proposed comprising ahollow body member having a passageway therethrough for receiving apipe, and gripper means positioned circumferentially in the passageway,comprising contractile rings, split locking rings, moveable resilientrings, and the like. Exemplary of such proposals are those described inGB2035495, GB2166508, GB2180310, GB2035495, GB1334339, GB1153177,GB1266603, U.S. Pat. No. 3,534,776, U.S. Pat. No. 3,600,010, U.S. Pat.No. 3,692,336 and U.S. Pat. No. 4,068,866, the entire disclosures ofwhich are incorporated herein by reference for all purposes.

Many of the prior proposals incorporate gripping means comprising anannular ring which can move axially within the passageway and ispositioned within a circumferential tapered channel in the hollow bodymember, so that, when forces act on the pipe tending to disengage itfrom the body member, the annular ring moves axially along the taperedchannel so as to grip the pipe with a wedging action.

Typically such annular gripper rings give rise to problems in practice.For example, where the ring is a split resilient ring, it is difficultto insert it into the circumferential tapered channel, and when insertedit can easily become twisted so that it impedes the insertion of thepipe into the hollow member. In such circumstances, if the gripper ringbecomes jammed, the pipe joint is useless and must be discarded. Even ifthe gripper ring does not jam, if it becomes twisted, or does not rideup to the top of the tapered channel properly, the external surface ofthe pipe may still become scored and damaged on entry.

According to the present invention, the above difficulties are obviatedby the use of a segmented gripper means.

In a first aspect, the present invention provides a pipe jointcomprising a hollow body member having a passageway therethrough forreceiving a pipe, a segmented gripper means positioned in a firstcircumferential tapered channel in the hollow body member and moveableaxially within the passageway, the arrangement being such that, in use,when forces are applied tending to separate the pipe from the hollowbody member the segmented gripper means can move axially along thetapered channel into gripping engagement with the pipe.

Preferably the pipe joint is provided with sealing means which ispreferably located in a second circumferential channel in the hollowbody member.

The pipe joint can be used, for example, to join a pipe to another pipe,in a pipe coupling, or to join a pipe to a pipe fitting, or to anotherpiece of apparatus. The invention can be used to join pipes ofdissimilar materials, and, in a particularly preferred embodiment, thepipe joint can form part of a novel electrofusion fitting as will bemore particularly described hereinafter.

The invention can be used to join pipes made from metal or plastics, butis particularly useful for joining plastic pipes, for example those usedfor carrying fluids such as gas or water, in, for example, utilitiesservice pipe systems.

The hollow body member is preferably of generally cylindrical shape, andcan, for example, comprise a generally cylindrical sleeve made frommetal or plastics materials, or a combination thereof. Preferably thebody member is made from a plastics material, which may be moulded,extruded, or otherwise formed into the desired shape. Suitable plasticsmaterials include, for example, those made from olefin polymers,especially alpha olefins, such as, for example, homo-polymers andco-polymers of alpha olefins, for example, ethylene, propylene, butene-1or 4-methylpentene-1; olefin co-polymers, for example,ethylene-propylene co-polymers; polymers of substituted olefins, forexample, chlorinated polyethylenes; and polymers and co-polymers ofvinyl monomers such as vinyl esters, for example ethylene-vinyl acetateand ethylene-ethyl acrylate co-polymers.

Preferably the passageway in the hollow body member is dimensioned toreceive the pipe in relatively close fitting engagement. The hollow bodymember preferably is provided with two or more axially spaced apartcircumferential channels for receiving respectively the segmentedgripper means and one or more sealing means. The passageway can, ifdesired, be provided with a widened bore at its outlet, to facilitatethe entry of the pipe into the passageway.

In preferred embodiments of the invention, the two or morecircumferential channels are arranged such that the firstcircumferential tapered channel accommodating the segmented grippermeans is located upstream of the channel or channels accommodating thesealing means, that is to say, the first circumferential tapered channelaccommodating the segmented gripper means is nearer to the entrance ofthe passageway.

In the specification, by segmented gripper means is meant a grippermeans comprising two or more segments which are preferably separate,although they could be pivotally joined or articulated at their ends. Apreferred segmented gripper means according to the present inventioncomprises an annular ring, which can be divided into two or moreseparate segments. Preferably the segmented gripper means comprisesthree such segments.

The segments of the gripper means are preferably made from a resilientmaterial, which can be a metal or plastics material. For joining softerplastics pipes, the segmented gripper means may comprise, for example, apolyolefin polymer material such as polyethylene, but for pipes madefrom harder materials the segmented gripper means is preferably madefrom an engineering plastics material, such as, for example, an acetalresin, or from a resilient metal such as spring steel.

The segmented gripper means, when assembled, preferably has afrusto-conical outer surface which is co-operable with thefrusto-conical surface of the first circumferential tapered channel.

Preferably the segmented gripper means comprises a ring formed from twoor more, and preferably three, separate segments, each of which is asegment of a circle having a larger radius than the largest radius ofthe first circumferential tapered channel. The segments, if desired, canbe of uniform cross-section along their length, but preferably, they arewider at their ends and, if desired, also at their mid-portions, inorder to provide a loose interference fit when the pipe is inserted intothe passageway of the hollow body member.

The segments may have smooth inner surfaces or, alternatively, the innersurfaces may be roughened, or provided with teeth, to grip the outersurface of the pipe. Where such teeth are provided, these are preferablyangled such that they permit easy entry of the pipe into the passageway,but can bite into the outer surface of the pipe in order to resist theremoval thereof from the hollow body member.

In order to insert the segments of the gripper means into the firstcircumferential tapered channel, it is only necessary to press them intothe channel, for example, by hand, so that they are resiliently deformedto a tighter radius than their free radius, the deformed radius lyingbetween their undeformed radius and the maximum radius of the taperedbore of the channel, whereupon each segment exerts a force on the endsof the adjacent segment or segments when no pipe is inserted in thepassageway of the hollow body member, and each of the segments arethereby resiliently retained in the first circumferential taperedchannel. In a preferred embodiment, the segmented gripper meanscomprises a ring having three segments, and the segments are assembledby resiliently deforming two of the segments to conform to the radius ofthe tapered bore of the circumferential tapered channel and springingthe third segment into the gap between the first two.

The spring action of the segments of the segmented gripper meansprovided by the force exerted by the ends of each on the other, tends toretain the gripper means segments at the top of the taper of the firstcircumferential channel, thereby allowing ready entry of the pipe intothe hollow body member passageway.

The sum of the circumferential length of the segments of the grippermeans is less than the circumferential length of the firstcircumferential tapered channel at its widest bore (at the top of thetaper) and, also, preferably less than the circumferential length of thefirst circumferential tapered channel at its narrowest point. Preferablythe arrangement is such that, as a pipe is pushed into the passageway ofthe hollow body member, it first contacts a central portion of eachsegment such that the centred portion is forced outwards towards thefrusto-conical surface of the first circumferential tapered channel andthe radius of curvature of each segment is reduced. Frictionalengagement between at least the centre portions of the segments as thepipe is received in the passageway thereby maintains the segments of thegripper means at the wider bore end of the circumferential taperedchannel. In this position the deformed segments tend to separate, suchthat there are small gaps between their adjacent ends.

However, should forces be applied tending to separate the pipe from thehollow body member, the frictional forces between the segments of thesegmented gripper means and the pipe tend to move the segments axiallyalong the first circumferential tapered channel towards the narrowerbore end thereof, until they are wedged between the frusto-conicalsurface of the first circumferential tapered channel and the outersurface of the pipe. The teeth, if present, then grip into the pipefurther increasing the strength of the connection. In this lockingposition, it is preferable that the ends of the segments do not toucheach other, that is to say, the abovementioned gaps, though reduced, arestill present.

If, for any reason, the frictional forces between the segments and thepipe outer surface are insufficient to drag the segments along the firstcircumferential tapered channel, it is possible to increase theinterference fit of the segments with the pipe by reducing the radius onthe inner face of each segment relative to its outer face and moving thecentre of the arc of the radius on the inner face closer to the segmentso that additional frictional force is applied at localised regions atthe ends of each segment.

In an alternative embodiment, inwardly-directed projections may beprovided at the mid-point and ends of each segment to provide a greaterinterference with the pipe.

In preferred embodiments of a pipe joint according to the invention,there is provided a sealing means located in a second circumferentialchannel in the hollow body member. The second circumferential channelcan be tapered or otherwise profiled to accommodate the sealing meanswhich is preferably an annular seal, made from, for example, anelastomer or a resilient polymeric material. Preferably the sealingmeans comprises an annular ring, the ring having a substantiallyU-shaped, V-shaped, or C-shaped cross section lying on one side, so thatthe arms of the U-shaped, V-shaped, or C-shaped cross section arepressed tightly respectively against the inner surface of the secondcircumferential channel and the outer surface of the pipe when the pipeis inserted into the passageway. Typical such sealing rings aredisclosed in GB940833, GB1283489, GB2016630, GB2109078, and EPA073083,the entire disclosures of which are incorporated herein by reference forall purposes. Very good results have been obtained using an annularsealing ring made by Bode and Fosheda and sold under the trade name BODASEAL.

In a particularly preferred embodiment, the pipe joint of the inventioncan form the inner portion of an electrofusion coupling. In thisembodiment, the outer surface of the hollow body member is smooth, andis formed from a fusion bondable plastics material. The pipe joint isinserted into an electrofusion coupler, which comprises a hollow bodymember having an electrical heating element embedded in or adjacent toits inner wall. Typically, such heating elements comprise a coil ofelectrical resistance wire connected to terminals mounted on the outersurface of the electrofusion coupler. The body member of theelectrofusion coupler comprises a fusible plastics material, forexample, an olefin polymer or co-polymer. When the pipe joint of theinvention is inserted into the electrofusion coupler and the electricalheating element is energised, a fusion bond is formed between the outersurface of the pipe joint and the inner surface of the body member ofthe electrofusion coupler.

The pipe joint of the invention thereby enables pipes made of dissimilarmaterials to be coupled together by a combination of mechanical andelectrofusion techniques.

Certain embodiments of pipe joints according to the invention will nowbe described, by way of example only, with reference to the accompanyingDrawings in which:

FIG. 1 shows, in sectional side elevation, a pipe joint according to theinvention assembled in an electrofusion coupler;

FIG. 2 shows a section along the line X--X of FIG. 1;

FIG. 3 shows a plan view of a segmented gripper ring for use in a pipejoint according to the invention;

FIG. 4 shows a detail of the profile of a segment of the gripper ring ofFIG. 3;

FIG. 5 shows a plan view of a first gripper ring segment modified togive improved frictional grip;

FIG. 6 shows a plan view of a second gripper ring segment modified togive improved frictional grip; and

FIG. 7 shows, in sectional side elevation, an in-line pipe connectionmade using a pipe joint and electrofusion coupler as shown in FIG. 1.

Referring firstly to FIG. 1, the pipe joint, illustrated generally at 1,comprises a cylindrical sleeve member 2, made from polyethylene, havinga passageway 3 for the insertion of a pipe (not shown). The bore of thepassageway 3 is widened with a taper 4 to permit easy insertion of thepipe. Within the passageway 3 there are situated first and secondcircumferential tapered channels 5 and 6, accommodating respectively asegmented gripper ring 7 and a V-shaped elastomeric sealing ring 8. Thesegmented gripper ring 7 is provided with circumferential teeth 9, 10,11 and is made of a hard material, for example, acetal resin, so thatthe teeth can bite into the outer surface of, for example, apolyethylene pipe.

As shown in FIG. 1, the pipe joint 1 is inserted into an electrofusioncoupler 12 having an electrical heating element (not shown) in the formof spiral coils of resistance wire embedded adjacent to the innersurfaces 13, 14 thereof, and connected to terminals 15, 16. Theelectrofusion coupler 11 is a standard reducing fitting supplied byUponor Limited under the trade mark EASIGRIP.

Referring to FIGS. 2 and 3, the segmented gripper ring comprisessegments 20, 21 and 22, each being shaped in the form of a segment of acircle whose diameter is greater than the larger diameter of the taperedchannel 5. This can readily be seen from FIG. 3 where the circumferenceof the tapered channel 5 is indicated by broken line 23.

In order to assemble the pipe joint, the elastomeric sealing ring 8 isfirst inserted into the second circumferential tapered channel 6 bygentle pressure. The elastomeric sealing ring is of the type sold byBode and Fosheda under the trade mark BODA SEAL.

Next, the gripper ring is assembled by inserting two of the segments,20, 21, 22 into the tapered channel 5 and deflecting them back to theradius of the tapered bore. The third segment can then be sprung intothe remaining gap. When in position in the channel 5, the gripper ringsegments 20, 21 and 22 are such that the ends of each exert a springforce on the next thereby retaining the gripper ring in the channel. Theeffect of the force is to urge the segments of the gripper ring towardsthe larger diameter end 15 (see FIG. 1) of the tapered channel 5.

A detail of a segment of the gripper ring is shown in FIG. 4, in whichthe inwardly and rearwardly directed teeth 9, 10, 11 are illustrated ona larger scale.

FIGS. 5 and 6 show two gripper ring segments modified to give improvedfrictional grip. In FIG. 5, the segment 30 has an inner surface 31 witha radius 32 that is smaller than the radius 34 of the outer surface 33.The centre 37 of the arc of radius 32 is offset along its centre linewith respect to the centre of the arc of radius 34 and lies nearer tothe segment 30. The result is that the width B of the segment at an end35 is greater than the width A of the segment at its midpoint 36.Preferred width variations for different internal pipe joint diametersare as follows:

    ______________________________________           Diameter                  B - A    ______________________________________            90 mm 0.8 mm           125 mm 1.0 mm           180 mm 1.4 mm    ______________________________________

FIG. 6 shows another embodiment of a modified gripper ring segment 40,which is provided with inwardly directed projections 41, 42 at its endsand a similar inwardly directed projection 43 at its mid-point. Theprojections have a length of about 6 mm and a height which is preferablydetermined by the internal pipe joint diameter as follows:

    ______________________________________           Diameter                  B - A    ______________________________________            90 mm 0.8 mm           125 mm 1.0 mm           180 mm 1.4 mm    ______________________________________

An in-line pipe connection made using a pipe joint according to theinvention and an electrofusion coupler, as illustrated in FIG. 1, isshown in FIG. 7.

In use, when a pipe 50 is inserted into the passageway 3, it contactsthe mid-portions 24, 25 and 26 of the segments 20, 21 and 22, deflectingthem towards the tapered outer surface, and towards the larger diameterend, of the tapered channel 5. When the pipe is fully inserted in bodymember 2, its outer surface is sealed by the elastomeric sealing ring 8and held by the gripper ring teeth 9, 10 and 11. If the pipe 50 attemptsto move out of the body member 2 the segments 20, 21, 22 of the gripperring 7 tend to follow the pipe axially for a short distance until theybecome wedged between the tapered outer surface 51 of the taperedchannel 5 and the outer surface of the pipe 50. At this position, anyfurther movement causes the circumferential teeth 9, 10, 11 of thegripper ring 7 to bite harder into the outer surface of the pipe therebyarresting further outward movement.

The outer surface of the pipe joint 1 can readily be fused to the innerwall 13 of the electrofusion coupler 12 by connecting an appropriatesource of electrical energy to the electrical terminals 15 and 16 inconventional fashion. At the same time, a second pipe 52 made from afusible plastics material can be fusion bonded to the inner wall 14 ofthe electrofusion coupler 12. The standard reducing electrofusionfitting is thereby able to connect a pipe made from, for example, aninfusible material, which is normally not capable of electrofusion, to afusible plastics pipe.

The reader's attention is directed to all papers and documents which arefiled concurrently with or previous to this specification in connectionwith this application and which are open to public inspection with thisspecification, and the contents of all such papers and documents areincorporated herein by reference.

All of the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and/or all of the steps ofany method or process so disclosed, may be combined in any combination,except combinations where at least some of such features and/or stepsare mutually exclusive.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings), may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

The invention is not restricted to the details of the foregoingembodiments. The invention extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

We claim:
 1. A pipe joint comprising a hollow body member having apassageway therethrough for receiving a pipe, a segmented gripper meanspositioned in a first circumferential tapered channel in the hollow bodymember and moveable axially within the passageway to grip a pipeinserted in the hollow body member when forces are applied tending toseparate the pipe from the hollow body member, characterised in that thesegmented gripper means comprises a segmented annular ring, each segmentof which is a segment of a circle having a larger radius than thelargest radius of the first circumferential tapered channel, firstcircumferential tapered the ends of the segments bearing against oneanother in the channel.
 2. A pipe joint according to claim 1, which isprovided with a sealing means located in a second circumferentialchannel in the hollow body member.
 3. A pipe joint according to claim 1,in which the hollow body member comprises a generally cylindrical sleevemember (2) made from metal or plastics materials, or a combinationthereof.
 4. A pipe joint according to claim 1, in which the hollow bodymember is provided with one or more axially spaced apart circumferentialchannels accommodating respectively one or more sealing means.
 5. A pipejoint according to claim 4, in which the one or more circumferentialchannels are arranged such that the first circumferential taperedchannel accommodating the segmented gripper means is located upstream ofsaid one or more circumferential channels accommodating the one or moresealing means.
 6. A pipe joint according to claim 1, in which thesegmented gripper means comprises an annular ring divided into threesegments.
 7. A pipe joint according to claim 1, in which the segments ofthe gripper means are formed from a resilient metal or plasticsmaterial.
 8. A pipe joint according to claim 1, in which the segmentedgripper means, when assembled, has a frusto-conical outer surface whichis cooperable with a frusto-conical surface of the first circumferentialtapered channel.
 9. A pipe joint according to claim 1, in which thesegments are of generally uniform cross section along their length, butare wider at their ends, and optionally also at their mid portions. 10.A pipe joint according to claim 1, in which the segments of thesegmented gripper means are provided with teeth in order to grip theouter surface of the pipe, the teeth being angled such that they permiteasy entry of the pipe into the passageway, but can bite into the outersurface of the pipe in order to resist the removal thereof from thehollow body member.
 11. A pipe joint according to claim 1, in which thesegmented gripper means comprises an annular ring having three segments,and the segments are assembled by resiliently deforming two of thesegments to conform to the radius of the tapered bore of thecircumferential tapered channel and springing the third segment into thegap between the first two.
 12. A pipe joint according to claim 1, inwhich, as a pipe is pushed into the passageway of the hollow bodymember, it first contacts a central portion of each segment such thatthe central portion is forced outwards towards the surface of the firstcircumferential tapered channel and the radius of curvature of thesegments is reduced.
 13. A pipe joint according to claim 1, in which thesum of the circumferential lengths of the segments of the gripper meansis less than the circumferential length of the first circumferentialtapered channel at its widest bore, and less than the circumferentiallength of the first circumferential tapered channel at its narrowestpoint.
 14. A pipe joint according to claim 1, in which, when thesegments of the segmented gripping means are moved along the taperedchannel into gripping engagement with the pipe, the adjacent ends of thesegments do not all touch each other.
 15. A pipe joint according toclaim 9, in which the radius on the inner face of each segment isreduced relative to its outer face and the centre of the arc of theradius on the inner face is closer to the segment so that additionalfrictional force is applied to the pipe at the ends of each segment. 16.A pipe joint according to claim 9, in which each segment is providedwith inwardly-directed projections at its midpoint and at its ends. 17.A pipe joint according to claim 2, in which the sealing means comprisesan annular seal formed from an elastomer, or a resilient polymericmaterial.
 18. A pipe joint according to claim 17, in which the sealingmeans comprises an annular seal having a substantially U-shaped,V-shaped, or C-shaped cross section lying on one side, so that the armsof the U-shaped, V-shaped, or C-shaped cross section are pressedrespectively against the inner surface of the second circumferentialchannel and the outer surface of the pipe, when the pipe is insertedinto the passageway.
 19. A pipe joint according to claim 1, adapted tobe inserted into an electrofusion coupler.
 20. A pipe joint according toclaim 1, in combination with said electrofusion coupler.
 21. Anelectrofusion coupling comprising a pipe joint according to claim 1.